1. Field of the Invention
This invention relates to barrel locks, specifically to means for inducing relative rotation between a barrel lock and a key.
2. Problems Addressed by the Invention
Barrel locks are used to secure meter rings like the one shown in U.S. Pat. No. 4,702,093 (DeWalch, 1987), as well as a variety of other locking hardware. In the present disclosure, the term xe2x80x9clocking hardwarexe2x80x9d is used to refer to any device which is secured by a barrel lock. A barrel lock, as defined in the present disclosure, is commonly characterized as having a generally cylindrical case with a head portion, a smaller diameter shank portion, and a shoulder portion interposed between the head and shank portions. The shank portion includes retaining means, usually a pair of retractable steel balls, to prevent extraction of the lock from the meter ring or other locking hardware when the lock is locked. Usually barrel locks are removed from the locking hardware when they are unlocked. In many cases removal of the lock is required for opening the locking hardware.
Many barrel locks, such as the one described in U.S. Pat. No. 4,289,000 (Nielsen, 1981), rely on axial movement of the key to actuate the lock. Although the operation of axially actuated locks is independent of lock rotation, these locks have a relatively small number of possible key codes, are often easy to pick, and require the use of a rather large and cumbersome key. To overcome these difficulties, barrel locks have been developed which are actuated by rotation of the key relative to the lock. In the present disclosure, this type of lock will be referred to as a xe2x80x9crotationally actuated barrel lockxe2x80x9d.
The generally cylindrical shape of most barrel locks allows them to rotate freely within the locking hardware. Although rotationally actuated barrel locks have many advantages, their rotation within the locking hardware can potentially cause a problem during lock actuation. Whenever the torque required to unlock the lock is greater than the torque required to rotate the lock within the locking hardware, the entire lock will rotate with the key. Since no relative rotation occurs between the lock and the key, the lock remains locked. In this situation, the user is clearly in need of some means to induce the relative rotation of the lock and key.
3. Discussion of Prior Art
In order to provide background information so that the present invention may be completely understood in its proper context, reference is made to the following articles of prior art. The first article of prior art comprises an O-ring installed on the smaller diameter shank portion of the barrel lock, abutting the shoulder formed at the transition to the larger diameter head portion. When the barrel lock is locked or unlocked, the user applies an axial force on the lock via the key. The O-ring is compressed between the shoulder on the lock case and an internal shoulder in the locking hardware, creating a frictional force to inhibit rotation of the barrel lock. This approach is unreliable, due to its dependence on the condition of the O-ring, the presence of moisture, dirt or oil, and other factors which affect the frictional characteristics of the component surfaces.
A second method for inducing relative rotation of the barrel lock and key involves the user grasping a portion of the lock itself, to keep it from rotating while the key is turned. In order for this method to be used, some portion of the lock must be made accessible to the user. This is usually accomplished either by designing the locking hardware so that it does not completely cover the lock, or by elongating a portion of the lock so that it extends beyond the locking hardware, as shown in Swiss Pat. No. 474,653. However, whenever the lock grasping method is used, the exposed portion of the lock makes the whole system more susceptible to tampering and vandalism. For this reason, it is common for the entire lock case to be completely shielded and protected by the locking hardware, thereby denying the user access to the lock.
A third article of prior art is the set screw shown in U.S. Pat. No. 5,085,063 (Van Dyke, et al., 1992). Although the set screw prevents rotation of the lock within the locking hardware, it also prevents axial movement of the lock, thus making it difficult and time consuming to remove the lock from the locking hardware. Since lock removal is necessary for proper hardware operation in many barrel lock applications, the usefulness of the set screw alternative is limited.
Whatever the precise merits, features, and advantages of the above cited articles of prior art, they do not achieve or fulfill the purposes and objects of the present invention as set forth below.
Objects of the Invention
Accordingly, several objects and advantages of the present invention are:
(a) to provide a means for inducing the relative rotation of a barrel lock and key, in particular when the lock is substantially encased by the locking hardware.
(b) to provide a means for inducing the relative rotation of a barrel lock and key which allows for easy removal of the lock from the locking hardware.
(c) to provide a means for inducing the relative rotation of a barrel lock and key which will operate reliably.
Other and further objects, advantages and features of the present invention will become apparent from a consideration of the following discussions and drawings describing various embodiments of the invention.
Brief Physical Description
The preferred embodiment includes a rotationally actuated barrel lock, a key for opening the lock, and a generally cylindrical sleeve rotatably mounted about the key. The sleeve is also free to slide axially along the key within preset limits. Lock actuation is characterized by rotation of the key relative to the lock. During actuation of the lock, a set of prongs on the sleeve engages a complementary set of notches on the barrel lock, thereby non-rotatably coupling the barrel lock to the sleeve. By grasping the sleeve, the user can prevent rotation of the sleeve and the lock while turning the key, and thus actuate the lock.
Present Invention Vs. Prior Art
The present invention is more reliable than the O-ring of the prior art, because the interlocking means used to couple the barrel lock to the sleeve operates independently of frictional forces. The O-ring of the prior art relies entirely on friction to prevent rotation of the lock, and is therefore dependent upon the condition of the O-ring and the presence of surface contaminants. The present invention is an improvement over the lock grasping method of the prior art in that the present invention does not require any portion of the lock to extend beyond the locking hardware, where it would be vulnerable to tampering and vandalism. The present invention is also a more desirable alternative than the set screw of the prior art because the present invention allows for complete and easy removal of the lock from the locking hardware. The set screw of the prior art prevents any axial movement of the lock, and thus hinders easy removal of the lock.
How the Invention Fulfills the Objects
The present invention provides a means for inducing the relative rotation of a barrel lock and key when the key is turned. This means comprises a sleeve rotatably mounted on the key. This sleeve non-rotatably couples the lock via complementary prongs and notches on the sleeve and the lock, respectively. The user can easily prevent the lock from rotating by holding the sleeve stationary when the key is turned. Because the notches are on the top of the lock, the present invention can be used even when the lock is encased on all sides by the locking hardware. Furthermore, the present invention does not prevent axial movement of the lock, and therefore allows for easy removal of the lock from the locking hardware.